1. Field of the Invention
Aspects of the present invention relate to a proton-conductive material comprising a new polymer compound, a proton-conductive electrolyte comprising the proton-conductive material, and a fuel cell employing the proton-conductive electrolyte. In some embodiments the present teachings comprise a proton-conductive material comprising a new polymer compound that has high proton conductivity, has good heat resistance, and chemical stability due to good membrane formation properties. Another aspect of the present invention is that the proton-conductive material can be prepared by fewer process operations, and/or under mild conditions, a further aspect of the present invention includes a proton-conductive electrolyte comprising the proton-conductive material, and a fuel cell employing the proton-conductive electrolyte.
2. Description of the Related Art
Fluorinated polyethylene sulfonic acids are widely and industrially used for salt electrolysis, sea water desalination, water treatment, and forming proton-conductive membranes, etc. Examples of proton-conductive membranes include NAFION® membranes, FLEMION® membranes, ACIPLEX® membranes, DOW® membranes, etc. The membranes are obtained by synthesis and polymerization employing a variety of processes. However, these membranes contain fluorine, and are also expensive.
In addition, polystyrene sulfonic acids are often used to form an ion exchange resin, or an ion exchange membrane for water treatment, and the polystyrene is sulfonized in a severe condition of fuming sulfuric acid, thereby having a negative impact on the environment.
Japanese Patent Laid-open Publication No. 2005-171087 discloses poly(sulfonate alkoxy phenylene oxide) that has high proton conductivity, and excellent film formation properties, and can be synthesized under mild conditions compared to polymers containing various sulfonic acid groups. The film can be useful as a proton-conductive electrolyte membrane for an inexpensive fuel cell.
However, a sulfonic acid group of the poly(sulfonate alkoxy phenylene oxide) starts to decompose at around 200° C. Therefore, the sulfonic acid group may decompose when the corresponding fuel cell is used for a long period of time. As a result, proton conductivity is degraded.